Influence Of Caveolin-1 Down-regulation On DNA Damage Repair And Autophagy Induced By X-ray Irradiation In Hepatoma Carcinoma Cells SMMC-7721

Primary liver cancer is a serious hazard to human health cancer.In clinical treatment,radiation in local control of liver cancer patients is one of the main important therapy ways.However the radiation resistance made the higher cure dose higher than the tolerance dose,On this occasion,liver cancer radiotherapy could’t reach the ideal treatment effect.So improving the radiation sensitivity becomes a key to raise curative effect of liver cancer.In recent years,research shows that Caveolin-1 as an important structural protein of caveolae,involved in several signal transduction pathways,at the same time,Caveolin-1 plays important roles in autophagy of cancer cells,and then affects the cellular radiosensitivity.On the basis of these findings,In this system,we first develope a stable low expression of Caveolin-1 gene knockdown cell model in human hepatoma cells(SMMC-7721)employing siRNA technology,and then investigate the cell survival ability,cell cycle variation,DNA damage repair,autophagy of cancer cell and related signal transduction factor expression after being exposured to X-ray radiation.We have tried to elucidate the relationship between Caveolin-1 expression and the radiation sensitivity of human hepatoma cells,DNA damage repair and autophagy.This study aims to reveal the role of Caveolin-1 as a platform for marker proteins of the cell membrane signal transduction in response to cellular radiation injury and autophagy,and to provide experimental basis for the clinical treatment.The results as follows:(1)Successfully establish Caveolin-1 gene stable low hepatoma carcinoma cells.After construction of Caveolin-1 siRNA restructuring psiRNA-hHlzeo G2 plasmid and cell transfection,we identify the expression of Caveolin-1 was down-regulated by 80%.(2)Caveolin-1 gene silencing increased radiosensitivity of hepatoma carcinoma cell.It shown that cells survival rate are reduced after After exposure to 0-10 Gy X radiation,and the survival rate of 7721 cell declined significantly compared with 7721 cell(P<0.01).(3)Caveolin-1 gene silencing reduce DNA damage repair,and the mechanism has relations with ATM repair pathway activation and weakened the ability to combine MDM2 Caveolin-1.After exposure to 5Gy X radiation,the expression of γH2AX、p-ATM and p53 higher(P<0.01),and the interaction between Caveolin-1 and Mdm2 is increased.They were significantly lower than the control cells after Caveolin-1 gene down-regulation.(4)Caveolin-1 gene silencing increased cell Autophagy.After 5Gy X irradiation,the ratio of LC3B-Ⅱto LC3B-Ⅰin 7721 KD is higher than in 7721 cells.Conclusion:Caveolin-1 plays an important role in radiosensitization of hepatoma carcinoma cells.Caveolin-1 gene silencing influences on the response to DNA damage repair and autophagy,and then decreases the radiation resistance of hepatoma carcinoma cells.